Embryo Folding

This animation shows a mid-sagittal section of the folding of the embryonic disc beginning week 3 of development.

Embryo (midline section) shown to the left and early placenta to the right. The embryonic disc dorsal (ectoderm) top and ventral (endoderm) bottom. Cranial end of disc to the left and caudal end of disc to the right.

Note also the early cardiac region shown at the cranial end of disc and the allantois at the caudal end of disc extending into the connecting stalk.